The positive progress made toward greater unity among divided Christians during the 50 years since the Second Vatican Council should not be taken for granted, German Cardinal Walter Kasper suggested in an address on Saturday.

He made the comments at an international Ecclesiological Investigations conference held between Washington on May 21-24.

He asked: “What will the future of ecumenism be in the 21st century?” The 20th century “aroused great hopes” for Christian unity, he noted. Yet, in the current century “clear signs of fatigue have become apparent.”

Cardinal Kasper is the past president of the Pontifical Council for Promoting Christian Unity.

Pope Francis, in his very first Sunday Angelus message, mentioned he was reading the cardinal’s book on mercy, which in English is titled “Mercy: The Essence of the Gospel and the Key to Christian Life,” published by Paulist Press.

“That book did me a lot of good,” Pope Francis remarked.

The 82-year-old cardinal spoke to a session on ecumenism during the Ecclesiological Investigations conference. The session took place in the Washington National Cathedral, the Episcopal Church’s cathedral in the US capital.

Despite the progress made, especially the rediscovered sense of “Christian fraternity” among Christians of different churches, “significant questions remain,” said Cardinal Kasper.

He explained that the fundamental issue, “and for many the dead end, in which dialogue is at the moment at a standstill, is the question: What is the concrete goal of the ecumenical endeavour? What does unity mean or what does full communion mean in concrete terms?”

Cardinal Kasper cautioned that “if we are not in agreement on where we are going, there is a great danger that we will disperse in different directions and in the end find ourselves further apart than at the start.”

The conference he addressed was co-sponsored by Jesuit-run Georgetown University in Washington, Marymount University in Arlington, Virginia, Washington National Cathedral and the Ecclesiological Investigations international network of theologians, religious leaders, ministers and other scholars and researchers.

Conference participants included Catholics, Anglicans, Protestants, Jews, Muslims and members of other world religions. Their theme, “Vatican II: Remembering the Future,” prompted them to look beyond 2015 in exploring Vatican II’s promise.

One way Christians of differing denominations can approach the future is by following the lead of Pope Francis and remembering the Gospel, Cardinal Kasper proposed. He said, “A church which goes back to its apostolic origins goes also forward to the future.”

In the history of Christianity, the Gospel always was “the fundamental motif of renewal movements,” the cardinal said. In this regard, he added, Pope Francis “stands in the best tradition of church renewal movements.”

Cardinal Kasper characterised the Gospel as “the same at all times and in all places” but “always new.” Pope Francis “speaks of the eternal novelty of the Gospel and means by that its inexhaustible riches,” said the cardinal. The Pope means, moreover, that the Gospel “in its original freshness bursts all categories and cliches.”

A return to the Gospel involves more than returning to the Jesus of history, the cardinal told Catholic News Service. It also leads to a focus on the risen Lord, who sends the Spirit now. Cardinal Kasper stressed that the Gospel provides a common basis for ecumenism.

The Reverend Gary Hall, dean of Washington National Cathedral, discussed Vatican II’s “rediscovery of the primacy of baptism” in a presentation to the cathedral session of the Ecclesiological Investigations conference.

Vatican II “ushered in a process of rethinking baptism” as a sacrament in which all ministries are grounded, he said. After Vatican II, Christians across a denominational spectrum expanded their understanding of baptism and its implications for ministries in the church and the world.

Rev. Hall told CNS that Vatican II was “a seminal moment,” but not only for Catholics. It had a large impact, for example, on his seminary education through its emphasis on the importance of Scripture study.

Cardinal Kasper also turned attention to baptism, noting its importance as a sacrament Christians share. He pointed out that through “one baptism, all the baptized are members of the one body of Christ,” even if “deeply wounded by the existing divisions.”

The “most important fruit” of ecumenism is not found in “the multitude of documents” that emerged over the past 50 years, but in “the mutual recognition of one another as Christians,” he said. “What we have in common,” he added, “is more than that which divides us.”

This, the cardinal said, “has already led to a new ecclesial reality that has so far been too little considered: a still incomplete but nevertheless profound spiritual community in one God and Father, in the Lord Jesus Christ and in the one body of Jesus Christ.”